"""
The HALT operation.
Halts execution of the computer by stopping the clock.
"""
from itertools import product
from ..language_defs import (
INSTRUCTION_GROUPS,
SRC_REGISTERS,
DEST_REGISTERS,
MODULE_CONTROL,
FLAGS,
instruction_byte_from_bitdefs,
)
from ..operation_utils import assemble_instruction, match_and_parse_line
from ..data_structures import get_machine_code_byte_template
_NAME = "HALT"
[docs]def generate_microcode_templates():
"""
Generate microcode for the HALT operation.
Returns:
list(DataTemplate): DataTemplates for all the HALT microcode.
"""
instruction_byte_bitdefs = generate_instruction_byte_bitdefs()
flags_bitdefs = [FLAGS["ANY"]]
control_steps = [
[MODULE_CONTROL["CLOCK"]["HALT"]]
]
return assemble_instruction(
instruction_byte_bitdefs, flags_bitdefs, control_steps
)
[docs]def generate_instruction_byte_bitdefs():
"""
Generate bitdefs to specify the HALT instruction.
Returns:
list(str): Bitdefs that make up the instruction_byte
"""
return [
INSTRUCTION_GROUPS["STORE"],
SRC_REGISTERS["SP+/-"],
DEST_REGISTERS["SP+/-"],
]
[docs]def parse_line(line):
"""
Parse a line of assembly code to create machine code byte templates.
If a line is not identifiably an HALT assembly line, return an
empty list instead.
Args:
line (str): Assembly line to be parsed.
Returns:
list(dict): List of instruction byte template dictionaries or an
empty list.
"""
match, signature = match_and_parse_line(line, _NAME)
if not match:
return []
instruction_byte = instruction_byte_from_bitdefs(
generate_instruction_byte_bitdefs()
)
mc_byte = get_machine_code_byte_template()
mc_byte["byte_type"] = "instruction"
mc_byte["bitstring"] = instruction_byte
return [mc_byte]